This invention relates to the weft inserting mechanism of a vertical weaving machine. In particular, the invention concerns stabilization of the entry and exit rapiers during the weft insertion operation.
The rapiers in a weaving machine are typically composed of an elongated tubular section having a thread carrying head which travels into and out of the warp shed during the weft inserting operation. Depending on the amount of support provided along the length of the rapier, the rapier head experiences varying degrees of random movements in combinations of horizontal and vertical directions transverse to the longitudinal movement of the rapier while the rapier is traveling in the warp shed. In standard looms having a generally horizontal configuration the rapiers are supported along their entire length during the weft inserting operation since they rest on a warp sheet supported by the lay of the machine while traveling in the shed. The situation is considerably different in weaving machines having a vertical configuration such as those currently being developed for weaving triaxial fabric of the type disclosed in U.S. Pat. No. Re. 28,155 and U.S. Pat. No. 3,874,422 both issued to Norris F. Dow. Weaving machines constructed with a vertical configuration do not readily lend themselves to providing mechanical supports for the rapiers as is done in standard horizontal looms. In vertical weaving machines the rapiers are cantilevered in such fashion that the weft carrying head is totally unsupported and is susceptible to random transverse movement while traveling in the shed. In order to attain successful transfer to the weft yarn from the entry rapier to the exit rapier it is essential that the rapiers come precisely together. The inherent instability of the cantilevered rapiers can result in misalignment of the rapiers at the weft transfer point and consequently the exit rapier fails to grip the weft yarn. This results in a flaw in the fabric. A similar result occurs if the rapier runs into an out of place warp yarn. Since the rapier head is relatively free, it will generally be deflected by the warp yarn and consequently there is a missed transfer. When there is a missed transfer the machine is stopped by a stop motion device and the weft yarn must then be inserted manually. To obtain high efficiency the number of stops must be minimized. It is also possible that the entry and exit rapiers can collide resulting in substantial damage to the rapiers. It is thus desirable to obtain a degree of rapier stabilization which assures accurate mating of the rapiers and successful transfer of the weft yarn from the entry rapier to the exit rapier.
Increased rapier stabilization can be obtained by using larger, stiffer rapier tubes or an I-beam cross-section for the rapier but this would result in an undesirable increase in cost, weight and power requirements. It is also possible to provide a guide means for the rapiers on the machine itself but this would unduly complicate the machine construction. The invention disclosed herein provides an inexpensive means for stabilizing the rapiers which does not require any changes in the machine construction.